Does anyone know how I can get the Wii U to just format one partition of my HDD. I'd like to use the second partition for my backup games on my Wii. This way, I don't have to keep changing hard drives.

Sorry, it's not possible.
Nintendo designed it to delete everything from the drive, all partitions are removed and a big single partition (whithout a partition table) is created for WiiU format.

There were some tests done by a user, but it would (not possible right now) involved launching a program on PC each time to display/hide a partition by faking the HDD size.
You can't keep it connected to the console and use both partition at the same time.

So much for wanting to use it for Wii ISO images. Not worth it if I have to unplug it every time, unless someone hacks the firmware preventing the format prompt.

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I hope someone can do this. I do not want to be prompted to format my drive every time I start up my Wii U. I use it for the vWii backup games. My ultimate hope was to have two partitions, one for the vWii and one for Wii U.

I hope someone can do this. I do not want to be prompted to format my drive every time I start up my Wii U. I use it for the vWii backup games. My ultimate hope was to have two partitions, one for the vWii and one for Wii U.

Click to expand...

I'm sure part of the reason Nintendo doesn't allow for partitions alongside with a proprietary file system is to curtail its use with illicit activity. The prompt is controlled via firmware and once that's been hacked, it's just a matter of time before that algorithm is disabled.

I don't know about linux partition, but I supposed that if it finds a partition table, it doesn't care what the partition types are, it just prompt to format the HDD.

Another users reported that he is using two HDD at the same time.
One 3TB (for vWii, fully ignored by WiiU as it's not compatible)
and a one less than 2TB, formated in WiiU format, ignored by vWii.

Though, I've read that if there are two HDD connected at the same time, the ports were all disabled in vWii (it could be a user's wrong report because his drives didn't work fine, or not enough power etc.)

I make some test with my Flash drive, in first i formate it in fat 32, insert in WiiU, WiiU ask me about format this drive. In second, i fill this flash drive with 0x00 bytes, insert in WiiU, and WiiU dont't ask about format. In setting if i click on Format, WiiU write then flash can be formated, but don't ask about format if it's start with flahs drive connected
P.S. Flash Drive size is 4Gb

I make some test with my Flash drive, in first i formate it in fat 32, insert in WiiU, WiiU ask me about format this drive. In second, i fill this flash drive with 0x00 bytes, insert in WiiU, and WiiU dont't ask about format. In setting if i click on Format, WiiU write then flash can be formated, but don't ask about format if it's start with flahs drive connected
P.S. Flash Drive size is 4Gb

I made some tests with my flash drive. First I format it in fat32, insert in the WiiU, and the WiiU asks me about formatting this drive. Second, I filled this flash drive with 0x00 bytes, then inserted in the WiiU, and the WiiU doesn't ask about formatting the drive. In System Settings if I click on Format, WiiU says the flash drive can be formatted, but it doesn't ask about format formatting if the WiiU starts with the flash drive connected.
P.S. Flash Drive size is 4Gb

Make another test:
format my usb flash in FAT32 and insert in WiiU , WiiU ask me about format drive. With WinHEX i change one of 2 bytes in address 0x01FE and 0x01FF to any number and WiiU don't ask about format drive, but USB loader in vWii mode also write me "USB device not found" (i use USB loader GX). But Windows on my PC work with this USB flash fine, it's see the flash in FAT32 format, and chkdsk also don't write me about any error after check'it